Cognitive radio (CR) is a promising technology that facilitates efficient use of the radio spectrum. In cognitive radio systems, unlicensed users (secondary users) can use a spectrum that has been pre-allocated to licensed users (primary users) when the spectrum is not being used by the primary user.
In some cognitive radio systems, when the secondary users try to access spectrum resources that are pre-assigned to the primary users, the secondary users need to first sense the spectrum and then access the spectrum according to the sensing results. To guarantee the priority of the primary transmission as well as to maintain the transmission of the secondary link, ideally, the secondary user needs to have an accurate and reliable sensing capability in a limited sensing period. In particular, a higher detection probability is desired in order to afford a higher protection level to the primary system while a lower false alarm probability offers a better opportunistic access to secondary users.
Cooperative relaying is a well-known technique that can significantly improve the reliability of the transmission between the source node and the destination node. In relaying networks, a source node is assisted by one or multiple intermediate nodes, referred to as the relay nodes, to deliver information to the destination through one or multiple hop(s). Different relaying (cooperative) protocols have been studied considering how a relay node processes its received signal and forwards such a processed signal to another relay or destination. Such relaying protocols include amplify-and-forward (AF), decode-and-forward (DF), compress-and-forward (CF).
Embodiments described herein may provide a cooperative spectrum sensing method for cognitive relay systems which achieves a trade-off between the sensing performance and the complexity in terms of information feedback.